I think it's more like:

Reason:
-it's easy and convenient to copy
Moral Excuses:
-everyone does it
-publishers make undeserved profit from their product


I don't think many people feel strongly that they should have a right to free music, but it's much easier to download than to go and buy a CD. It's also easier to download off a free site than one where you have to register and register bank details.

That said, I think that had iTunes and other online music distrubution come into play at an earlier stage, then more people today would be using iTunes and less people piracy.